1. Field of the Invention:
This invention relates to treadmills and, more particularly, to an improved treadmill apparatus which is formed with a trampoline-like surface, supported by an improved multiple position peripheral spring support, that is resilient enough to minimize shock when the foot of an exerciser engages the treadmill surface but rigid enough not to interfere with the normal walking, jogging or running motions.
Treadmills utilize an endless moving belt that allows an individual to walk, jog or run in place. Treadmills are useful not only for exercise purposes, but for rehabilitation programs and medical testing such as the popular "stress test." There is also a demand for treadmills in indoor health clubs since many clubs are not able to build a running track and such a treadmill provides the capability of a well rounded exercise program.
Treadmills traditionally are formed with a thin endless belt which travels over a supporting surface such as a metal plate so that the belt can withstand the weight of the individual using it. The belt in such a design has a tendency to wear because of the frictional contact between the plate and belt. The metal support plate forms a rigid surface that can create various injuries such as "stone bruise" or "shin splints" because of its hard, unyielding surface. Another possible way of supporting the belt is to provide rollers under the belt. This construction is not totally desirable because the rollers provide an uneven exercise surface.
Thus, exercising on a treadmill with a rigid support surface underneath the belt is similar to exercising on a hard surface because the impact of the feet of the exerciser and the support surface for each step which is taken. This tends to exert undue strain on the legs, which is a common cause of leg problems for joggers and runners and is particularly bothersome for patients who are undergoing a rehabilitation program.
Several treadmill devices are the subject of U.S. Patents. The Jones U.S. Pat. No. 2,315,485, issued Apr. 6, 1943, entitled "Exercising Device," shows an exercising machine having a moving belt, end rollers supporting the belt at its end portions, and an adjustment for varying the tension of the belt.
The Volk U.S. Pat. No. 921,755, issued May 18, 1909, illustrates a treadmill-type device constructed of cross slats, each carrying anti-friction rollers. Other treadmill devices including the Haracz U.S. Pat. No. 3,628,654, entitled "Vacuum Belt Conveyor;" the Hagan U.S. Pat. No. 3,689,066, entitled "Treadmill Exercising Device With Yieldable Belt Support;" and German Patent No. 2,503,118, entitled "Movable Endless Band Apparatus For Physical Training, Containing Profiled Rails Connected To Band."
Applicants are the owners of prior U.S. Pat. No. 4,548,405, issued Oct. 22, 1985, entitled "Treadmill With Trampoline-Like Surface," which discloses a treadmill having a belt surface supported at its lateral edges with springs and between front and rear rollers.
The present invention provides an improvement to these above-referenced patents in that an improved spring geometry supports the lateral edges of the belt in both lateral and longitudinal directions by means of a pair of spaced apart angularly extending springs which contact the belt at spaced positions. Further, Applicants' invention provides an improved treadmill apparatus which may utilize a secondary surface, spaced below the belt upper surface, that limits the vertical deflection of the belt during use. The secondary surface maintains stability of the belt when it is used by very heavy persons or by runners that exercise vigorously.